Essential metal ions alter the lactoferrin binding to the erythrocyte plasma membrane receptors

The effect of metal ions at a concentration of l0^-8 to l0^-5 M [using their salts: ZnCl₂, CdCl₂, LiCl, CuSO₄, NiSO₄, A1₂(SO₄)₃, (NH₄)₂MoO₄ on the lactoferrin (Lf) binding to the erythrocyte membrane receptors was studied. In the absence of metal ions, Scatchard’s analysis showed the existence of two kinds of binding site: one with high affinity and low capacity, and the another with low affinity and high capacity. All these metals, excluding Zn²⁺ and Cd²⁺, at a concentration 10^-5 M decreased the affinity of Lf binding (Ka₁) to the high-affinity receptors. In the presence of Zn²⁺ and Cd²⁺, only the lowaffinity binding site was found. Significant inhibition on the affinity (Ka₂) of the low-affinity class of receptors showed Zn²⁺, Al³⁺, and Mo⁶⁺. Depending on their concentration (10^-8-10^-5 M), these ions enhanced to a different extent, the binding capacity of the both types receptors, but the effect did not correspond to the applied doses. Several explanations of the mechanism for influence of the metal ions on the Lf-receptor interaction is discussed.